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[35.238.199.243]) by smtp.gmail.com with ESMTPSA id m13sm3189371ilq.51.2021.05.16.19.05.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 16 May 2021 19:05:13 -0700 (PDT) Date: Mon, 17 May 2021 02:05:11 +0000 From: Dennis Zhou To: trix@redhat.com Cc: tj@kernel.org, cl@linux.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] percpu: initialize best_upa variable Message-ID: References: <20210515180817.1751084-1-trix@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210515180817.1751084-1-trix@redhat.com> Authentication-Results: imf06.hostedemail.com; dkim=none; dmarc=fail reason="SPF not aligned (relaxed), No valid DKIM" header.from=kernel.org (policy=none); spf=pass (imf06.hostedemail.com: domain of dennisszhou@gmail.com designates 209.85.166.46 as permitted sender) smtp.mailfrom=dennisszhou@gmail.com X-Stat-Signature: ea6anintktrptxrwdoqy99ccpzrew1kr X-Rspamd-Queue-Id: BF16BC0007CA X-Rspamd-Server: rspam02 X-HE-Tag: 1621217113-491519 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hello, On Sat, May 15, 2021 at 11:08:17AM -0700, trix@redhat.com wrote: > From: Tom Rix > > Static analysis reports this problem > percpu.c:2945:6: warning: Assigned value is garbage or undefined > upa = best_upa; > ^ ~~~~~~~~ > best_upa may not be set, so initialize it. > > Signed-off-by: Tom Rix > --- > mm/percpu.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/mm/percpu.c b/mm/percpu.c > index a257c3efdf18b..6578b706fae81 100644 > --- a/mm/percpu.c > +++ b/mm/percpu.c > @@ -2916,6 +2916,7 @@ static struct pcpu_alloc_info * __init __flatten pcpu_build_alloc_info( > * Related to atom_size, which could be much larger than the unit_size. > */ > last_allocs = INT_MAX; > + best_upa = max_upa; > for (upa = max_upa; upa; upa--) { > int allocs = 0, wasted = 0; > > -- > 2.26.3 > I think the proper fix would be: best_upa = 0; for (...) { } BUG_ON(!best_upa); upa = best_upa; If you're fine with this I'll make the changes and apply it to for-5.13-fixes. Can you also tell me what static analysis tool produced this? I'm just a little curious because this code hasn't changed in several years so I'd have expected some static analyzer to have caught this by now. Thanks, Dennis